ActiveRecord Monkey Patch to make Rails 5 dump DB agnostic format (1 of 2)

schema_dumper_1_of_2.rb

# config/initializers/active_record/schema_dumper.rb
#
# DANGER, Will Robinson!!!
#
# This is a monkey patch for Rails 5.0 ONLY
#
if Rails.version !~ /^5.0/ # code taken from 5.0.6

            puts "\n
--------------------------------------------------------------------------------
WARNING: you are using Rails version #{Rails.version}
         Please double check that the monkey-patch for Schema Dumping still works!
         see: \"#{__FILE__}\"
--------------------------------------------------------------------------------
"

else

  module ActiveRecord
    class SchemaDumper #:nodoc:

      def table(table, stream) # code taken from 5.0.6
        columns = @connection.columns(table)
        begin
          tbl = StringIO.new

          # first dump primary key column
          pk = @connection.primary_key(table)

          tbl.print "  create_table #{remove_prefix_and_suffix(table).inspect}"

          case pk
          when String
            tbl.print ", primary_key: #{pk.inspect}" unless pk == 'id'
            pkcol = columns.detect { |c| c.name == pk }
            pkcolspec = @connection.column_spec_for_primary_key(pkcol)
            if pkcolspec.present?
              pkcolspec.each do |key, value|
                tbl.print ", #{key}: #{value}"
              end
            end
          when Array
            tbl.print ", primary_key: #{pk.inspect}"
          else
            tbl.print ", id: false"
          end
          tbl.print ", force: :cascade"

          # DO NOT DUMP TABLE OPTIONS!!!!
          #
          # table_options = @connection.table_options(table)
          # if table_options.present?
          #   tbl.print ", #{format_options(table_options)}"
          # end

          tbl.puts " do |t|"

          # then dump all non-primary key columns
          column_specs = columns.map do |column|
            raise StandardError, "Unknown type '#{column.sql_type}' for column '#{column.name}'" unless @connection.valid_type?(column.type)
            next if column.name == pk
            @connection.column_spec(column)
          end.compact

          # find all migration keys used in this table
          keys = @connection.migration_keys

          # figure out the lengths for each column based on above keys
          lengths = keys.map { |key|
            column_specs.map { |spec|
              spec[key] ? spec[key].length + 2 : 0
            }.max
          }

          # the string we're going to sprintf our values against, with standardized column widths
          format_string = lengths.map{ |len| "%-#{len}s" }

          # find the max length for the 'type' column, which is special
          type_length = column_specs.map{ |column| column[:type].length }.max

          # add column type definition to our format string
          format_string.unshift "    t.%-#{type_length}s "

          format_string *= ''

          column_specs.each do |colspec|
            values = keys.zip(lengths).map{ |key, len| colspec.key?(key) ? colspec[key] + ", " : " " * len }
            values.unshift colspec[:type]
            tbl.print((format_string % values).gsub(/,\s*$/, ''))
            tbl.puts
          end

          indexes_in_create(table, tbl)

          tbl.puts "  end"
          tbl.puts

          tbl.rewind
          stream.print tbl.read
        rescue => e
          stream.puts "# Could not dump table #{table.inspect} because of following #{e.class}"
          stream.puts "#   #{e.message}"
          stream.puts
        end

        stream
      end

    end
  end

end